NAME

B::Bytecode - Perl compiler's bytecode backend

SYNOPSIS

        perl -MO=Bytecode[,OPTIONS] foo.pl

DESCRIPTION

This compiler backend takes Perl source and generates a platform-independent bytecode encapsulating code to load the internal structures perl uses to run your program. When the generated bytecode is loaded in, your program is ready to run, reducing the time which perl would have taken to load and parse your program into its internal semi-compiled form. That means that compiling with this backend will not help improve the runtime execution speed of your program but may improve the start-up time. Depending on the environment in which your program runs this may or may not be a help.

The resulting bytecode can be run with a special byteperl executable or (for non-main programs) be loaded via the byteload_fh function in the B module.

OPTIONS

If there are any non-option arguments, they are taken to be names of objects to be saved (probably doesn't work properly yet). Without extra arguments, it saves the main program.

-ofilename: Output to filename instead of STDOUT.
--: Force end of options.
-f: Force optimisations on or off one at a time. Each can be preceded by no- to turn the option off (e.g. -fno-compress-nullops).
-fcompress-nullops: Only fills in the necessary fields of ops which have been optimised away by perl's internal compiler.
-fomit-sequence-numbers: Leaves out code to fill in the op_seq field of all ops which is only used by perl's internal compiler.
-fbypass-nullops: If op->op_next ever points to a NULLOP, replaces the op_next field with the first non-NULLOP in the path of execution.
-fstrip-syntax-tree: Leaves out code to fill in the pointers which link the internal syntax tree together. They're not needed at run-time but leaving them out will make it impossible to recompile or disassemble the resulting program. It will also stop goto label statements from working.
-On: Optimisation level (n = 0, 1, 2, ...). -O means -O1. -O1 sets -fcompress-nullops -fomit-sequence numbers. -O6 adds -fstrip-syntax-tree.
-D: Debug options (concatenated or separate flags like perl -D).
-Do: Prints each OP as it's processed.
-Db: Print debugging information about bytecompiler progress.
-Da: Tells the (bytecode) assembler to include source assembler lines in its output as bytecode comments.
-DC: Prints each CV taken from the final symbol tree walk.
-S: Output (bytecode) assembler source rather than piping it through the assembler and outputting bytecode.
-m: Compile as a module rather than a standalone program. Currently this just means that the bytecodes for initialising main_start, main_root and curpad are omitted.

EXAMPLES

        perl -MO=Bytecode,-O6,-o,foo.plc foo.pl

        perl -MO=Bytecode,-S foo.pl > foo.S
        assemble foo.S > foo.plc
        byteperl foo.plc

        perl -MO=Bytecode,-m,-oFoo.pmc Foo.pm

BUGS

Plenty. Current status: experimental.

AUTHOR

Malcolm Beattie, mbeattie@sable.ox.ac.uk

DISCLAIMER

We are painfully aware that these documents may contain incorrect links and misformatted HTML. Such bugs lie in the automatic translation process that automatically created the hundreds and hundreds of separate documents that you find here. Please do not report link or formatting bugs, because we cannot fix per-document problems. The only bug reports that will help us are those that supply working patches to the installhtml or pod2html programs, or to the Pod::HTML module itself, for which I and the entire Perl community will shower you with thanks and praises.

If rather than formatting bugs, you encounter substantive content errors in these documents, such as mistakes in the explanations or code, please use the perlbug utility included with the Perl distribution.

--Tom Christiansen, Perl Documentation Compiler and Editor

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